EUnit eats my stack trace !!!

fib.erl

-module(fib).
-export([fib/1]).
-include_lib("eunit/include/eunit.hrl").

%% this call a undef function in erlang module
fib(a) -> erlang:lists_to_atom("a");

fib(0) -> 1;
fib(1) -> 1;
fib(N) when N > 1 -> fib(N-1) + fib(N-2).

fib_test_() ->
  [?_assert(fib(0) =:= 1),
    ?_assert(fib(1) =:= 1),
    ?_assert(fib(2) =:= 2),
    ?_assert(fib(3) =:= 3),
    ?_assert(fib(4) =:= 5),
    ?_assert(fib(5) =:= 8),
    ?_assertException(error, function_clause, fib(-1)),
    ?_assert(fib(31) =:= 2178309)
  ].

%% a error test 
fib_other_test_() ->
  [?_assert(fib(a) =:= "a")].


%% I'm trying this code in erlang shell.

> c(fib).
> {ok, fib}.
> eunit:test(fib).
fib:22: fib_other_test_...*failed*
::undef

====================================
  Failed: 1.  Skipped: 0.  Passed: 8.
error

%%